Wet or impregnated wipes are of wide application in several fields. For example, nonwoven fabric cloths are used for cleaning purposes and may be impregnated with waxes or other cleaning solutions. Wet wipes are also used for personal care and may contain detergents, perfumes or even cosmetic lotions or creams.
These products are normally made from cellulose-based raw materials (typically less than 50% cellulose), such as pulp, carded viscose/lyocell airlace or spunlace, cotton and the like, which are provided with absorbent properties.
High absorbent properties are necessary for the cloth to be moistened and to retain a sufficient amount of the type of solution of the desired type (detergent, cosmetic and so on).
The above raw material fibers are generally hydroentangled or firmly bonded and are wetted with a solution of detergent and/or perfume, so that they can be packaged ready for use.
Pulp, viscose and lyocell absorb high amounts of water into the fiber. A stack of wet wipes with these fibers tends to be dense and thus its height is less than for similar wipes containing thermoplastic fibers such as polypropylene and polyester. As wet wipes are commonly packed in flexible plastic packagings, a small stack of wipes will give customers a negative impression of the amount of material in the package. Additionally, a softer wipe is more desirable by the customer due to its better feel.
Moreover, a certain amount of polypropylene, polyester or the like is normally added to this kind of product. The presence of such thermoplastic materials in the composition of a wipe is contrary to the aim of providing biodegradable products.
Biodegradability is considered an important feature for a wet wipe. The nature of these products implies that they should be flushable. Therefore, it is normally required that a flushable product be biodegradable.
However, biodegradability is not the only requirement that should be ideally fulfilled when providing a flushable wipe. As waste waters are normally made to pass through pumps, particularly when they must move against the force of gravity, for example, when they reach wastewater treatment plants, the material should also be water dispersible to avoid blockage of such pumps by the solid mass.
Improved water dispersibility can be achieved, but unfortunately this occurs by sacrificing the strength of the material. Biodegradability implies a long period of exposure to environmental conditions but water dispersibility is needed quickly. While looking at known products on the market, a good balance between water dispersibility and mechanical strength is still a great and long-felt need in this field.
It should be noted that a mechanical stress on a sheet of nonwoven material develops along two preferential directions that are perpendicular one to the other: the MD (Machine Direction) and the CD (Cross Direction). The MD is the direction along which the material is processed: a high strength along this direction prevents the sheet from being torn during the production of the wipes. The CD direction, conversely, is the direction along which the wipe is dispensed by the packaging, i.e. the direction along which the customer pull the wipe out, as required by current packaging processes. A good strength along this direction is essential as well. It is therefore important that a good balance between MD and CD strengths is obtained. This is also a great and long-felt need in the nonwoven fabric industry.